TX 551 
.L2 
Copy 1 



\ 



U. S. DEPARTMENT OF ACxRICULTURE, 

OFFICE OF EXPERIMENT STATIONS, 
A. C. TKT'E, I):RErTOR. 



— ^i 



THE NUTRITION INVESTIGATIONS OF 

THE OFFICE OF EXPERIMENT STA 

TIONS AND THEIR RESULTS. 

By 
C. F. LANGWORTHY, 

III Ch<iriji' of Nutrition Jmrxtiijatimis. 



[Reprint from Annual Report of the Office of Ex})eiinieut Stations for 
the year ended June 30, PKXj.] 



^7 



tlNGTON :COVERNMENT PRINTING OFTICE : 1907 



^7 



CONTEXTS. 



Pag-e. 

Scope of the work 360 

Distribution of the work 363 

Some results of the nutrition investigations 364 

Distribution of food materials in the diet 364 

Dietary studies 366 

Digestion experiments 367 

Respiration calorimeter experiments 368 

Special studies of cereals, legumes, meat, fruits, and nut:^ 370 

Pedagogics of nutrition 371 

Conclusion 372 



II 



SEP C 1907 
D. ofD. 



THE NUTRITiOX INVESTIGATIONS OF THE OFFICE OF EXPERI- 
; MENT STATIONS AND THEIR RESULTS. 

"^ By C. F. Langworthy, 

In charge of Niitrition Tnrestiyations. 

In recent years the experimental study of yarioiis prol)lems con- 
nected with food and nutrition of man and domestic animals has been 
actiyely followed in the United States. Some of the work has been 
of a yery practical nature and some has been highly technical. 
Though they are not commonly considered together, the studies of the 
food of man and animals have much in common, for of course the 
physiological laws which underlie the nutrition of the animal body 
are essentially the same for all warm-blooded animals. Then, too, 
many experimental methods are common to both classes of inves- 
tigation, at least as regards the principles on which they are based, 
though it is needless to say that the details and the manner of using 
the methods are varied. A considerable part of this inquir}^ into 
the various food problems has been carried on in connection with the 
agricultural experiment stations which have been established in the 
United States during the last thirty j^ears and are now in operation 
in all the States and Territories of the Union with the exception of the 
Philippines. In the earlier years of the experiment station movement 
in this country investigations which had to do with food in a broad 
sense were quite largely confined to work with domestic animals. 
However, early in their history many of the experiment stations 
studied the nutritive value of grains and other foods used by man as 
well as various problems connected with the storage, handling, and 
transportation of food products and related questions, and after a 
time a number of them included studies of the food of man in their 
regular work. 

Studies of the nutritive value of different foods have been conducted 
in the United States for a great many 3-ears, but the first systematic 
attempt to investigate such problems dates from the investigations 
carried on by Prof. W. O. Atwater for the Smithsonian Institution and 
for the Massachusetts bureau of labor and statistics, and the nutri- 
tion investigations of the Office of Experiment Stations are a natural 
outgrowth of this enterprise, as Professor Atwater, who was the first 
director of the Office of Experiment Stations, early sought to include 
this work with the other lines followed. 

In 1894-5 Congress provided a special appropriation which enabled 
the Secretary of Agriculture to prosecute inquiries in this direction and 

359 



360 



KEFOET OF OFFICE OF EXPEEIMEISTT STATIONS. 



tlie work was later assigned to the Office of Experiment Stations. 
From the first the plan of cooperation with experiment stations, 
agricultural colleges, and other educational institutions and with 
philanthropic associations was followed in the belief that such a course, 
in which each party was a contributor, would yield the most satis- 
factory returns for a given investment. The sums which have been 
appropriated by Congress for the nutrition investigations of the 
Department of Agriculture have been since the beginning as follows : 

■ Appropriations for nutrition investigations. 







I 


iscn 


1 year. 


Amount. 




Fiscal j-e?.r. 


Amount. 


IvO'- 


^_ 








?1 0,000 
15, OtlJ 
15,000 
15, 000 
15. 000 
15.000 
17, ,500 


iOOl-2.... 
J 902-3.... 




S20.000 


189.-)- 










20,000 










i90;i-4 

1904-.T 


20.000 












20, 000 


IVI^- 










190,5-6 

1906-7 


20,000 


IQOO- 










20,000 


-1901 




















^ 





These amounts have been increased by contributions from other 
sources, some of which are not easily estimated in terms of money, 
since they consist in large part of the use of laboratories, apparatus, 
chemicals, and other facilities for research, the counsel and help of 
experts, and similar services. Some of the States, notably Connecticut 
and Illinois, have made special appropriations for the stud}^ of prob- 
lems relating to the food and nutrition of man, and a considerable 
number of the experiment stations, educational institutions, philan- 
thropic associations, and private individuals have donated sums of 
money to promote cooperative research. 

Until ill health prevented. Prof. W. O. Atwater was the chief of the 
nutrition investigations and was responsible for the plans and general 
oversight of the work. A large amount of experimental work was also 
carried on under his immediate supervision in Professor Atwater's 
laboratory in the chemical department of Wesleyan University, the 
Connecticut (Storrs) Experiment Station being a generous contributor 
to the enterprise. As time progressed and the correspondence and 
other business arrangements connected with the nutrition investiga- 
tions developed, it became evident that the enterprise as a whole should 
be centered in Washington, and at the beginning of the fiscal year 
1906-7 a division of nutrition investigations was established in the 
Office of Experiment Stations. 

SCOPE OF THE WORK. 

In the earlier years of the nutrition investigations many analyses of 
American food materials were made, as the data regarding the chem- 
ical composition of such food materials were comparatively hmited. 
Information along this line has, however, accumulated very rapidly 



NUTRITION INVESTIGATIONS AND THEIE RESULTS. 361 

as a result of studies carried on by different investigators, and data 
are now so abundant that studies of proximate composition of food 
materials no longer constitute one of the lines of work followed in the 
cooperative nutrition investigations of the Office. Dietary studies — 
that is, studies of the kinds and amount of food purchased, eaten, and 
wasted — were early recognized as of great importance, and a large 
number have been made in private families, schools, colleges, public 
institutions, and elsewhere under a variety of conditions and in widely 
separated regions. , 

No matter what its composition, food is of no use to the body 
unless it is digested, and it is natural that experiments should have 
been undertaken with a variety of food materials to leain how 
thoroughly they were assimilated by the body and to ascertain the 
effect of various methods of preparation and combination upon 
thoroughness of digestion. Furthermore, it is supposable that the 
occupation in which the subject is engaged, whether active or seden- 
tary, may have an influence upon the work of the digestive tract, 
and this question has also been studied. Many questions regarding 
the thoroughness of assimilation may be investigated with the aid 
of ferments under conditions which approximate those in the bod}', 
and a large number of such artificial digestion experiments have been 
carried on, particularly in studying ease and rapidity of digestion, a 
question which is very different from thoroughness of digestion, 
though the two are often confused in popular discussions of the 
subject. 

Variations in the excretion of nitrogen have long been regarded as 
indications of changes taking place in the body, and it has been a 
general custom of physiologists to study the balance of income and 
outgo of nitrogen. Such studies have formed a part of the nutrition 
investigations of the Department. Much more useful as a means 
of studying the food requirements of the body and other questions 
are determinations of the balance of carbon, oxygen, and hydrogen, 
as well as nitrogen, and determinations of the balance of income and 
outgo of energ}^. Such studies necessitate special apparatus, and a 
respiration calorimeter has been devised which is admirably adapted 
to the purpose for which it is designed and which, it seems fair to 
say, is so far the most perfect instrument of its type. The respiration 
calorimeter is of such a size that a man may remain in comparative 
comfort in the respiration chamber for a number of hours or days, 
and the measurements of income and outgo of matter and energy 
may be made with great accuracy. The determination of energy 
values of food and excretory products necessitates some special 
apparatus for measuring the heat of combustion of these materials, 
and in connection with the nutrition investigations a bomb calorimeter 
has been perfected which has proved very satisfactory. 



362 REPORT OF OFFICE OF EXPERIMENT STATIONS. 

Numerous studies have been undertaken of the changes brought 
about and losses sustained when foods of different sorts are cooked 
in different ways, the principal food materials included in this work 
being bread, vegetables, and meat. Canning and preserving fruits 
and vegetables may be regarded as special applications of cooking 
processes and much experimental work has been done along these 
lines with a view to the elaboration of satisfactory household methods. 
In general, it may be said that in connection with the different lines 
of work mentioned it has been necessary to devise and perfect experi- 
mental methods, as at the time the investigations were first under- 
taken the amount of work which had been done in the United States 
and elsewhere along similar lines was not very considerable. 

The same period which has witnessed the development of the 
nutrition enterprise has seen a great interest aroused in the teaching 
of home economics in schools and colleges, and nutrition is one of the 
main divisions included in this subject? As the nutrition investiga- 
tions have supplied a great deal of data which the teachers of home 
economics must use and as the Office was already closely identified 
with other educational enterprises, it was almost inevitable that the 
pedagogics of nutrition should receive attention and become an 
increasingly important part of the nutrition enterprise. 

The preparation of reports of investigations and popular summaries 
has also constituted an important feature of the work. 

The following table shows in graphic form the character and 
extent of the investigations which have been undertaken up to July 
1,1906: 

Cooperative nutrition investigations of the Office of Experiment Stations. 

I Number ! Number 
Line of work. 1 of inves- i of publi- 

tigations.! cations. 




Dietary studies 

Digestion experiments. 

Experiments on the effect of different circumstances on the income and outgo of 

nitrogen 

Eespiration calorimeter experiments 

Experiments on efl'ects of cooking on meats 

Experiments on losses in cool-ing vpgetatjles 

Investigations on changes and losses in bread making 

Special investigations , 

Compilation of data 

Preparation of popular summaries 



(a) 



a These investigations arc included in the publications reporting digestion experin-ents. 

In addition to the popular summaries and the technical bulletins 
included in the above table, a large number of briefer summaries 
have been prepared which have appeared in the series of farmers' 
bulletins entitled "Experiment Station Work," and for the last ten 
years the subject of food and nutrition has constituted one of the 
divisions of the Experiment Station Record, and abstracts of the 
current literature of the subject have appeared regularly. 



NUTKITIUN INVESTIGATIONS AND THEIR RESULTS. 363 

DISTEIBUTION OF THE WORK. 

The cooperative investigations of the Office of Experiment Stations 
have been carried on in a considerable number of institutions in 21 
States and Territories. The following brief summary arranged alpha- 
betically by States shows the localities in which the investigations 
have been prosecuted and the names of the cooperating institutions: 

Alabama. — Tuskes'ee Normal and Industrial Institute. 
......^ 

California. — University of California and California Agricultural Experiment Station . 

Connecticut. — Wesleyan University, Storrs Experiment Station, and Connecticut 
Bible Normal College. 
, Georgia. — University cf Georgia. 

Hawaii. — Hawaii Agricultural Experiment Station. 

Illinois. — Hull House, Chicago; Lewis Institute, Chicago; University of Illinois 
and University of Chicago. 

Indiana. — Purdue University. 

Maine. — University of Maine and Maine Agricultural Experiment Station. 

Maryland. — Baltimore Board of Charities and several public institutions in Balti- 
more. 

Massachusetts. — Massachusetts Institute of Technology, Boston; School of House- 
keeping, Boston; Wellesley College, Harvard University, and Bible Normal College, 
Springfield. 

Minnesota. — University of Minnesota and Minnesota Agricultural Experiment 
Station. 

Missouri. — University of Missouri. 

New Jersey. — New Jersey Agricultural Experiment Station. 

New Mexico. — New Mexico College of Agriculture and Mechanic Arts and New 
Mexico Agricultural Experiment Station. 

Neiv York. — Cornell University, Ithaca; Association for the Improvement of the 
Condition of the Poor, New York; New York Christian Alliance, New York, and 
Columbia University, New York. 

North Dakota. — North Dakota Agricultural College. 

Ohio. — Lake Erie College. 

Pennsylvania. — Philanthropic institutions, Philadelphia; Drexel Institute, Phila- 
delphia, and Pennsylvania College for Women, Pittsburg. 

Tennessee. — University of Tennessee. 

Vermont. — Vermont Agricultural Experiment Station. 

Virginia. — Hampton Normal and Agricultural Institute and LTniversity of Virginia, 
Charlottesville. 

Mention should also be made here of other investigations, which 
though not strictly a part of the cooperative inquiry yet are so closely 
related to it that they may be included in the summary. On behalf 
of the New York State Commission in Lunacy an extended series of 
dietary studies was undertaken in New York hospitals for the insane, 
under Professor Atwater's direction, as were also studies at the 
Elmira Reformatory, New York. For a number of years a sum of 
money has been granted by the Carnegie Institution for nutrition 
investigations at Middletown, Conn., and the work has been so 
planned that it supplemented the investigations there carried on 
under the auspices of this Department. 



3(34 REPORT OF OFFICE OF EXPKRIMFNT STATIOISrS. 

SOME RESULTS OF THE NUTRITION INVESTIGATIONS. 

It is difficult to measure the results of scientific investigations in the 
usual units, particularl}" when the data sought are in a considerable 
degree educational. When, as in the case of nutrition investigations, 
the results have also a very decided practical value and are capable 
of application on every farm and in every home, such an estimate of 
values is even more difficult. An idea of the returns given for the 
money invested may be gathered ftom the fact that since the institu- 
tion of the investigations in 1894-95, the total sum appropriated for 
this work has been $222,500. The total number of dietary studies 
made has been 485, each study having covered from three to thirty 
days. The total number of digestion experiments with men has been 
675, and in general each experiment has covered three days. Supple- 
menting this phase of the work 300 artificial digestion experiments 
have also been made. The total number of metabolism experiments 
has been 500, of which 88 have been experiments with the respiration 
calorimeter. These latter experiments have covered a total of 270 
experimental days. The total number of cooking experiments has 
been nearly 200. 

In addition to the above, a number of miscellaneous experiments 
have been made for the study of special problems, and the studies of 
pedagogical problems have likewise been numerous. 

As a result of the work 30 farmers' bulletins and 50 technical bulle- 
tins have been published, as well as numerous short popular summaries. 

In earlier statements " which have been published, attention has 
been called to some of the important results of nutrition investigations 
and at this time reference will be made to some of the later work. 

DISTRIBUTION OF FOOD MATERIALS IN THE DIET. 

Food habits vary greatly in different regions of the United States, 
and firticles of diet which are popular in one region are almost unknown 
in another. There are certain staple foods, however, such as meat and 
bread, which are obviously common to all regions, and it is generally 
conceded that such staple foods are the principal sources of nutritive 
material in the diet. The proportion of nutrients and energy which 
different classes of food materials supply in the diet of the average 
American family is a matter of considerable interest, and the table 
which follows and which is based on the results of 376 dietarj^ studies 
gives results which may be regarded as fairlj^ conclusive. 

« Some Results of Dietary Studies in the United States. Reprinted from U. S Dept. 
Agr. Yearbook, 1898. 

Scope and Results of the Nutrition Investigations of the Office of Experiment Sta- 
tions. Reprinted from'U. S. Dept. Agr., Office of Experiment Stations Ann. Rpt. 
1901. 

Investigations on the Nutrition of Man in the United States. U. S. Dept. Agr., 
Doc. No. 713. 



NUTRITION INVESTIGATIONS AND THEIR RESULTS. 



365 



Proportion of nutrients furnished by different food materials in average of 376 American 

dietary studies. 



Food materials. 


Total 

food 

material. 


Protein. 


Fat. 


Carbo- 
hydrates. 


ANIMAL FOODS. 

Beef and veal 


Per cent. 
7.2 

.9 
7.2 

.7 


Per cent. 
16.7 
2.1 
9.3 
1.6 


Per cent. 

13.2 

2.6 

42.1 

.9 


Per cent. 


Lamb and mutton 




Pork, including lard 




Poultry 








Total meats 


16.0 


29.7 


58.8 








Fish 


1.8 
2.1 


3.5 
4.1 


1.0 
2.9 




Eggs 








Butter 


1.6 
.3 

16.5 


.3 
1.0 

S.7 


16.6 
1.1 
8.0 




Cheese 




Milk and cream 


3 6 






Total dairy products 


18.4 
.2 


10.0 
.2 


25.7 
.2 


3 




3 








38.5 


47.5 


88.6 


3 9 






Wheat flour, patent 


12.2 
.1 

.1 
.3 

5.8 


19.4 
.1 

!5 
8.1 


1.5 


25.6 




2 


Wheat flour, graham 


.2 




.1 
1.6 


1 


Wheat ijread, patent . . . : 


12.4 




1 




.1 
.3 
.6 

8.7 
.2 
.5 
.3 

1.3 
.1 


.1 
.5 
.8 
10.1 
.2 

1.0 
.3 

1.6 
.1 




.2 


Crackers 


.5 
.9 
3.8 
.1 
. 5 


1 




1.4 




13.7 




.4 


Oatmeal and preparations 


1.1 




.9 


Rye 


.1 


3.1 




.5 








30.6 


43.0 


9.1 


, 61.8 








5.4 




17.5 






.1 












1.0 

.6 

12.5 

6.2 


2.9 

.4 

3.8 

1.6 


.2 

:z 

.5 


1.7 




.3 




8.3 




1.7 








20.3 


8.7 


1.0 


12.0 








3.8 
.6 


.3 
.2 


.3 
.1 


2.5 




1.2 






Total fruits 


4.4 


.5 


.4 


3.7 






Nuts . 






.1 
.2 






.5 
61.2 


.1 


.6 








52.3 


10.8 


95.7 








.3 


.2 


.6 


.4 








100.0 


100.0 


100.0 


100.0 







As will be seen from the above table, meats and poultry furnish 
not quite twice as much protein as all other animal foods together, 
and of the meats beef and veal together furnish in round numbers 
half of the protein supplied by the group of total meats. As sources 
of fat, meats furnish a little over twice as much as is supplied by all 
the other animal foods, pork being the most important of the meats 
in this respect. Dahy products are the most important animal 



366 REPURT OF OFFICE OF EXPERIMENT STATIONS. 

foods aside from meats, milk and cream together furnishing 10 per 
cent of the total protein and 26 per cent of the total fat of the diet. 
The animal foods furnish less than 5 per cent of the total carbohy- 
drates of the diet, this important food constituent being supplied 
almost exclusively by the cereals and other vegetable foods. It will 
be seen that the animal and vegetable foods are about equal in rank 
as sources of protein, some 52 per cent of the total protein being sup- 
plied by the vegetable foods, and the cereals furnishing 43 per cent 
are the most important members of the group. Little fat is furnished 
by vegetable foods, the group as a whole supplying only 11 per cent 
of the total amount in the diet. 

DIETAHY STUDIES. 

As a result of the numerous dietary studies and kindred investi- 
gations, wdiich form a part of the nutrition investigations, dietary 
standards have been proposed which experience has shown are satis- 
factory guides for the purchase of food supplies for families and 
institutions. These so-called standards have been reported and dis- 
cussed in earlier publications^ and need not be referred to further. 
How far these so-called standards represent the physiological demands 
of the body is a question which needs further investigation. 

In the case of actual energy requirements it is obvious that the 
amount required can not be less than the total quantity given off 
by a fasting man performing no external muscular work. This 
question and similar pliases of the subject have been studied with 
the respiration calorimeter and the results are referred to on 
page 368. As regards actual protein requirements, it seems very 
probable that the quantity varies with different physiological con- 
ditions and other circumstances and further investigations are needed 
before final deductions are warranted. 

The dietary studies have furnished a number of factors showing 
the amounts of food required by children of different ages and by 
women as compared with a man at moderate muscular work. These 
factors have been referred to in detail elsewhere." 

In earlier work no account was taken of the variations in food 
requii-ements in old age as compared with middle life. A number 
of the more recent dietary studies have been made in old-age homes 
and similar institutions, and as a result of this work the conclusion 
has been reached that the energ}^ requirements of men and women 
past middle life are practically the same per kilogram, body weight, 
and that such persons require nine-tenths as much food as an adult 
man in full vigor who is engaged in moderate muscular work. 

aJJ. S. Dept. Agr., Farmers' Bui. 142. 



KUTKITION INVESTIGATIONS AND THEIR RESULTS. 367 

One of the most obvious applications of the results of the nutrition 
investigations is found in the commissary department of large public 
institutions and in general in the feeding of large groups. Available 
data and experimental methods make it possible to examine the diet 
under such conditions and pass upon its adequacy and real value, as 
related to its cost, in much the same wdj that an expert accountant 
can pass upon the financial condition of any business enterprise. It 
is often possible to point out ways of checking waste and diminishing 
cost, or of improving the character of the food without additional 
expense. 

♦ As an illustration of the importance of nutrition investigations in 
]3ublic institutions it may be said that as a result of studies carried 
on for several years in large institutions in one of the Eastern States 
very considerable savings were affected, while the diet as a whole 
was improved. An examination of the accounts of one of these 
institutions showed a per capita saving of 13.7 per cent in the second 
year of the work over the per capita expenditure for the first year, 
and this reduction is all the more striking in view of the fact that 
during the year in which it was made the price of a large number of 
the food materials used had advanced very materially. A similar 
saving was effected in a number of institutions, and it seems fau* to 
conclude that the results were applicable to all the public institu- 
tions in the State. The total cost of the food supplied to all the 
institutions in the State at the time the studies were made was con- 
siderabl}' over $1,000,000, and if a similar saving had been made in 
all these institutions the total saving would have been more than 
$150,000 per year. 

In general, it may be said that the importance of appljdng the 
results of the nutrition investigations in the providing of food for 
public institutions, in the provisioning of camps and expeditions, in 
regulating the commissary department of the Army and Navy, and 
in determining the diet in schools and colleges, as well as in the home, 
is becoming more generally recognized each year as is shown by the 
man}' applications made to the Department for information along 
these lines and the numerous requests for aid in carrying on experi- 
mental dietary studies and other investigations. 

DIGESTION EXPERIMENTS. 

It has long been a custom with physiologists to calculate the 
digestibility of food of various kinds with the aid of average factors 
when it was not ])ossible to determine digestibility by actual experi- 
ments. Since it is the food digested and not the food eaten which 
is of special importance to the body, it is very often desirable in 
discussing ihe results of dietary studies to consider digestible nutri- 
ents rather than total nutrients, and the data desii-ed may be readdly 



368 



REPORT OF OFFICE OF EXPERIMENT STATIONS. 



calculated by the use of factors. The following table shows the 
factors for calculating the digestibility and fuel value of nutrients in 
a number of single foods and groups of food materials, which have 
been deduced from the large number of digestion experiments carried 
on in connection with the nutrition investigations of the Office. xV 
comparison of calculated results with data obtained from natural 
digestion experiments has shown that these factors are reasonably 
accurate, and it seems fau' to say that they are more satisfactory 
than any which have been hitherto proposed. 

Factors for calculating digestibility and fuel value of nutrients in food ynatcrials. 





Protein. Fat. Carbohydrates. 


En- 




Pro- 
por- 
tion 
of 
total 

in 
mix- 
ed 
diet. 


Di- 

gest- 
ibil- 
ity. 


Fuel value 
per gram. 


Pro- 
por- 
tion 
of 
total 

in 
mix- 
ed 
diet. 


Di- 
gest- 
ibil- 
ity. 


Fuel value 
per gram. 


Pro- 
por- 
tion 
of 
total 

in 
mix- 
ed 
diet. 


Di- 

gest- 
ibil- 
ity. 


Fuel value 
per gram. 


pro- 
por- 


Classes of food 
materials. 


To- 
tal 
nu- 
tri- 
ents. 


Di- 
gest- 
ible 
nu- 
tri- 
ents. 


To- 
tal 
nu- 
tri- 
ents. 


Di- 
gest- 
ible 
nu- 
tri- 
ents. 


To- 
tal 
nu- 
tri- 
ents. 


Di- 
gest- 
ible 
nu- 
tri- 
ents. 


of 
total 

ac- 
tually 

avail- 
able. 


Meat and fish 


P.ct. 
33 

4 
10 


P.ct. 
97 

97 
97 


Cals. 
4.27 
4.37 
4.27 


Cals. 
4.40 
4.50 
4.40 


P.ct. 
1 63 


P.ct. 
95 


Cals. 
9.03 
8.79 


Cals. 
9.50 
9.25 


P.ct. 
4 


P.ct. 

98 


Cals. 
3.82 


Cals. 
3.90 


P.ct. 

f 87 
\ 89 


Dairy products 


26 95 


[ 93 


Annual food (of 
mixed diet) 


47 


97 


4.27 


4.40 


89 


95 


8.93 ' 9.40 


4 


98 


3.82 


3.90 


89 




43 
3 


85 3. 87 


4.55 1 


if 62 


98 1 4.11 

97 1 4.07 

98 3.87 


4.20 
4.20 
3.95 
4.20 
4.20 
4.00 


91 


Legumes (dried) 


78 


3.47 


4.45 


■ 11 


90 


! 2 


83 
98 


Starches . . . 










8-37| 9-"50 ■..^:. 98i4.n 
10 1 95 ; 3.99 


98 


Vegetables 


6 
1 


83 
85 


3.11 
3.36 


3.75 
3.95 


91 


Fruit 


4 


90 


3.60 


88 








Vegetable food (of 
mixed diet) 


.53 


85 


3.74 


4.40 


1 
11 ; 90 


8.37 9.30 96 


97 


4.03 


4.15 


92 


Total food (of 
mixed diet).. 


103 


92 


4.05 


4.40 


100 


95 


8.93 


9.40 


100 


97 


4.03 


4.15 


91 



The table shows that the different food materials and groups of food 
materials vary greatly in the thoroughness with which they are assim- 
ilated. Meats of different sorts, as ordinarily prepared for the table, 
and indeed animal foods as a whole, are more completely digested 
than the common vegetable foods. Considering foods as a whole, 
96 per cent of the total organic material is digested and 91 per cent of 
the energy is available. In other words, on an average the body 
rejects only about 4 per cent of the nutrients and about 9 per cent of 
the energy supplied by the food. 

RESPIRATION CALORIMETER EXPERIMENTS. 

In conducting experiments of various kinds it is often very desirable 
to Iviiow every requirement of a subject engaged in mi scular work. 
The exact measurement of energy expenditure is time consuming and 
requires special apparatus, but with the aid of the factors deduced 
from the large number of experiments which have been made with 



NUTRnrON INVESTIGATIONS AND THEIR RESULTS. 369 

the respiration calorimeter the desired data may be calcuhited approx- 
imately. In the experiments referred to all grades of muscular 
activity have been tested, from the quiet of a fasting subject in deep 
sleep to the excessive muscular work of a professional bicycle rider 
whose powers were taxed to the utmost. When muscular work was 
performed other than that involved in the ordinary motions essential 
to eating and drinking and moving about in the respiration chamber, 
the muscular exercise consisted in operating a bicycle-like apparatus. 
The ease with which the wheel turned, and hence the severity of the 
work could be regulated, and the total amount of work performed 
could be accurately measured. 

It will be remembered that in discussions of body energy the amount 
of work is measured in terms of heat, the calorie being the commonly 
accepted heat unit. It should also be said that under usual conditions 
the total heat output during a given period affords an indication of 
the muscular activity of the body. When the body is quiet the heat 
output is small and when it is active the heat output is correspond- 
ingly larger, and the same is true of the carbon dioxid output. The 
average results of the experiments showing the output of carbon 
dioxid and heat for the body under the different conditions indicated 
are summarized in the table following, and with the aid of such data 
the total carbon dioxid and heat output, and hence the total energy 
output of the body, may be calculated. 

Average normal output of carbon dioxid and heat from the body. 



Conditions of muscular activity. 



Man a t rest, sleeping 

Man at rest, a waive, sitting up 

Man at light muscular exercise 

Man at moderately active muscular exercise. 

Man at severe muscular exercise 

Man at very severe muscular exercise 



Average quantities 


per hour. 


Carbon 
dioxid. 


Heat. 


Grams. 


Calories.. 


25 


t'5 


35 


leo' 


55 


170 


100 


2,0 


liO 


4;'0 


210 


(00 



It will be seen that the output not only of heat but also of carbon 
dioxid is very nearly proportional to the amount of muscular work. 
As an example of the way in which the data included in the table may 
be used for calculating the carbon dioxid and heat output under 
varying degrees of muscular activity the following may be cited: 

If a man sleeps eight hours per day, we may say that the carbon 
dioxid output during this period is approximately eight times the 
hourly amount eliminated during sleep by the average subject, or 
8 by 25 = 200. If he is at very severe muscular labor for eight hours, 
the carbon dioxid output would correspond to eight times the hourly 
amount for verv severe work, that is, 8 by 210= 1,680. And if the 



370 REPORT OF OFFICE OF EXPERIMENT STATIONS. 

remaining eight hours of the day were devoted to going to and from 
workj eating, sitting, etc., corresponding, say, to six hours of rest and 
two hours at hght muscular exercise, the carbon dioxid output will 
be six times the average amount eliminated per hour at rest, that is, 
6 by 35 = 210 grams, and two times the amount given off at light 
work, 2 by 55=110 grams. The total for the twenty-four hours 
would obviously be the sum of the quantities mentioned above, or 
2,200 grams. The heat eliminated in the twenty-four hours by men 
at very severe work may be likewise calculated by multiplying the 
time devoted to sleep, work, etc., by the average hourl}' output. In 
eight hours at sleep he would eliminate 520 calories (S by 65 = 520); 
in eight hours at work, 4,800 calories (8 by 600 = 4,800); in six hours 
of rest, 600 calories (6 by 100 = 600); and in two hours at light exer- 
cise, 340 calories (2 by 170 = 340); makuig a total for the twenty-four 
hours of 6,260 calories. 

The investigations made in connection with the respiration calorim- 
eter have furnished the most accurate records jet available of the 
normal diurnal variations in body temperature. A summary of this 
work and a discussion of the results which apply to problems of 
ventilation and other topics have been included in a recent publica- 
tion of the Department.'' 

SPECIAL STUDIES OF CEREALS, LEGUMES, MEAT, FRUIT, AND 

NUTS. 

As regards the results of special investigations, particular interest 
attaches to the studies of the digestibility ajid nutritive value of cereal 
products. The extensive investigations which have been made with 
different grades of flour have shown that when ground from the same 
lot of wheat the standard patent flour furnishes slightly less protein 
and mineral matter than the coarser flours but surpasses them in 
digestibility, and so may be fairly said to have a somewhat higher 
nutritive value pound for pound. The coarser flours have a somewhat 
laxative effect, which is commonly attributed to their bran content, 
and are useful in the diet in this way and for the variety which they 
give. In general, it may be said that flours of all sorts are nutritious 
and wholesome and among the most iinportant constituents of the 
diet. 

The investigations with cereal breakfast foods have shown that 
this class of goods so much used at the present time may constitute 
an important source of nutritive material, and that although the 
individual products differ less among themselves in nutritive material 
than is commonly supposed, as a whole the}^ are nutritious and 
directly comparable with flours of various tj^pes. The breakfast 
foods in which the coarser part of the grain has been removed have 

a\J. S. Dept. Agr. Yearbook, 1904, p. 205. 



NUTRITIOlSr INVESTIGATIONS AND THEIR RESULTS. 371 

much the same digestibilitv and total nutritive value pound for 
pound as the finer ifours, while those which retain the outer portions 
of the grain are more directly comparable with whole wheat and 
graham flours. 

Studies of the nutritive value of dried legumes have formed an 
important part of the nutrition investigations and have shown that 
in general these foods are well assimilated and may be made very 
important and economical sources of proteia-in the diet. Particular 
interest attaches to the results obtained with cowpeas, an important 
crop in the Southern States but little known in other regions. This 
legume, which possesses a distinctive and palatable flavor and may 
be cooked in a variety of ways, has been shown to closely resemble 
the more common beans and peas in digestibility and nutritive mate- 
rial, and is well worthy of general use. 

The investigations with fruits and nuts have demonstrated that 
these materials may be fairly regarded as economical sources of nutri- 
ents and energy, even when used in fairl}^ large amounts, and indicate 
that an appreciation of their real food value will greatly increase the 
amounts consumed. 

The extended investigations which have to do with the losses 
sustained when meat is cooked in various w^ays have showai that 
the loss is smaller in boiling than in roasting or frying. In general, 
the principal constituent lost in cooking is water, though when meat 
is boiled the amount of total substance which is removed may be as 
great as 20 per cent. Generally speaking, the smaller the cut the 
greater the percentage loss in cooking. The investigations have also 
shown that it is possible to control temperature and other factors so 
that uniform results may be obtained in the preparation of meat in 
the household or where it is cooked in larger ciuantities. 

PEDAGOGICS OF NUTRITION. 

An examination in detail of the courses in home economics given 
at the fifty or more agricultural colleges and other institutions receiv- 
ins: Government aid will show that the instruction in nutrition is very 
largely based on the results of the food investigations which have been 
carried on under the auspices of this Department. The same is true 
of the courses of instruction along this line given in high schools, 
universities, medical colleges, and other American educational insti- 
tutions. The number of text-books on food and nutrition has been 
comparatively limited, and at present a large proportion of teachers 
criving instruction in these subjects depend on Department publica- 
tions to supply this need. It is worthy of note that the newer text- 
books and handbooks of nutrition and physiological chemistry draw 
very largely upon the data furnished by these nutrition investigations, 
anci that the authors almost uniformly acknowledge their indebted- 
ness to the Department work and their appreciation of it. A similar 



LIBRARY OF CONGRESS 
872 REPORT OF OFFICE OF EXPERIME^ 11 

use is made in other countries of the results c n 014 339 773 7 

gations, and as an instance maybe cited the i ^^..^ 

of a considerable proportion of the nutrition publications in connection 
with the general movement for the dissemination of information 
' regarding food and nutrition in that country. 

As a part of the nutrition enterprise special attention is being paid 
to the collection of data of use to teachers and its arrangement in peda- 
gogical form, the work being carried on along the lines which have 
proved so successful in formulating courses in other branches of agri- 
cultural education. 

CONCLUSION. 

Attention has been directed in the foregoing pages to the lines 
which have been especially followed in carrying on the nutrition 
investigations of the Office of Experiment Stations, and some of the 
results of this important agricultural enterprise have been pointed out. 

As regards their origin, all foods, both animal and vegetable, are 
agricultural products. In the past the farmer was very commonly 
the distributor of his products, and the foods passed directly from the 
farm to the consumer. At the present day this is much less common, 
and most of the foodstuffs become articles of commerce before they 
reach the housewife, and in many cases are manufactured products, 
as they must pass through the mill, the dairy, the packing house, or 
other manufacturing institution before they are ready for use. 

Briefly stated, the chief object of the nutrition investigations is to 
secure the better utilization of these varied food products, and it 
seems fair to say that much has already been accomplished along 
this line. The housewife in the farm home or in the town has at her 
disposal a large amount of data regarding the composition, digesti- 
bility, and nutritive value of foods and their relative economy as 
sources of nutrients and energy, which will aid her in making a good 
use of her available food supply, and will help her to prepare for her 
family a diet which is rational and suited to their physical needs. At 
the same time, the investigations have demonstrated the importance 
of having the daily fare palatable, well cooked, and attractive, and 
have shown how such requirements ma}^ be met without undue cost. 
The manufacturer and the distributer of food products are likewise 
helped by the dissemination of knowledge concerning food materials 
and their preparation, for such knowledge means a greater develop- 
ment of the important commercial enterprises in which they are 
interested. And finally, the farmer, the cattle raiser, the dairyman, 
the market gardener, and all who are direct producers of food supplies 
are benefited, as a knowledge of the important facts regarding the 
comparative value of different foods can not fail to bring about 
improved standards of living, and hence a greater demand for the 
foodstuffs which they alone can supply. 

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